title: Prolactin regulation of dopaminergic neurons in the infundibulum pituitary stalk of bull calves.
abstract: The effects of elevated circulating concentrations of prolactin were examined on neurochemical estimates of activity of dopaminergic neurons in the infundibulum/pituitary stalk of Holstein bull calves (8-10 weeks of age). Activity of these neurons was estimated by measuring the accumulation of dihydroxyphenylalanine, the immediate precursor of dopamine, 15 min after an intravenous injection of the aromatic L-amino acid decarboxylase inhibitor, 3-hydroxybenzylhydrazine. Subcutaneous injections of the dopamine antagonist haloperidol every 6 hr for 1 day increased serum concentrations of prolactin and accumulation of dihydroxyphenylalanine in the infundibulum/stalk. Intravenous infusions of prolactin for 1 or 9 days increased accumulation of dihydroxyphenylalanine in the infundibulum/stalk, indicating that these neurons remain responsive to elevated prolactin for at least 9 days. It is concluded that elevated concentrations of prolactin in blood stimulate dopaminergic neurons in the infundibulum/pituitary stalk of bull calves. We speculate that these neurons may be analogous to the tuberoinfundibular dopaminergic neurons that regulate prolactin in rats.
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing 48824.
authors.forename: S A
authors.initials: SA
authors.lastname: Zinn
authors.forename: K J
authors.initials: KJ
authors.lastname: Lookingland
authors.forename: L T
authors.initials: LT
authors.lastname: Chapin
authors.forename: K E
authors.initials: KE
authors.lastname: Moore
authors.forename: H A
authors.initials: HA
authors.lastname: Tucker
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004298:Dopamine / Q000032:analysis* / Q000502:physiology; D006220:Haloperidol / Q000494:pharmacology; D007262:Infusions, Intravenous; D008297:Male; D009474:Neurons / Q000502:physiology*; D010902:Pituitary Gland / Q000032:analysis / Q000294:innervation*; D011388:Prolactin / Q000008:administration & dosage / Q000502:physiology*
chemical_list: D011388:Prolactin; D006220:Haloperidol; D004298:Dopamine